1. Field of the Invention
The present invention relates to optical semiconductor devices and, more particularly, to the coupling structure between the optical semiconductor laser diode and optical fiber of an optical semiconductor device and to the connection structure between the optical fiber and an external optical fiber.
2. Description of Related Art
The structure of conventional optical semiconductor equipment used in optical communications can be classified into two types, a pigtail type and a receptacle type. In the former type, a main body of the equipment has a pigtail cord and the equipment is connected to an external optical fiber by a connector. In the latter type, an external optical fiber is connected directly to an adapter of a main body of the equipment.
On the other hand, there are mainly two types of structures for optically coupling to an optical fiber the light emitted from an optical semiconductor laser diode. One type is a lens coupling structure in which a focusing lens is disposed between the end face of an optical semiconductor laser diode and an optical filler and they are coupled by the lens. Another type is a direct coupling structure for an optical fiber in which the optical fiber end face is disposed in the vicinity of the light-emitting end face of an optical semiconductor laser diode so that the emitted light is coupled directly to the core of the optical fiber.
Among conventional optical semiconductor equipment, the pigtail type has the problem that, when the optical semiconductor equipment is mounted on a printed board, the pigtail cord makes it difficult to handle the optical semiconductor equipment and to mount it automatically on the board. The pigtail cord also has the further problem that a mounting technique such as reflow soldering cannot be used and productivity cannot be increased from the standpoint of component mounting because the cover of the optical fiber does not have high heat-resistance.
On the other hand, the receptacle type does not have the above-described problems but, because an external optical fiber connected to the optical semiconductor equipment is difficult to position in the vicinity of the optical semiconductor laser diode because of its structure, the optical fiber direct coupling structure cannot be employed and only the lens coupling structure can be employed. Therefore, there is the problem that the optically coupled section cannot be reduced in size and a fastening mechanism becomes large and the device as a whole cannot be reduced in size. Further, there is the problem that it is difficult to fix the core position of an optical fiber housed in a ferrule of an optical fiber that is connected, according to the focusing position of the lens, and suitable optical coupling cannot be maintained.